1. Field of the Invention
The present invention relates to an internet telephone, and more particularly, to an internet telephone for correcting loss of a voice signal and a method for recovering voice data lost in the internet telephone.
2. Description of the Related Art
In making a call using the internet, the processing of a voice signal will now be described in brief.
At a sending part, an analog voice signal is firstly converted into a digital signal and then it is compressed and encoded. This compressed and encoded voice signal is transmitted to a receiving part in the form of a voice data packet.
At the receiving part, the compressed and encoded voice data packet is restored to the original digital signal and then is converted into the analog signal. The analog signal is outputted via a speaker. An internet telephone makes a telephone call by the above-described method in general.
FIG. 1 is a diagram illustrating the construction of an internet telephone in accordance with the conventional art.
As illustrated therein, the conventional internet telephone can operate as the sending part and the receiving part.
An internet telephone 120 corresponding to the sending part compresses and encodes a voice signal of a caller and transmits it in the form of packet data via the internet network 105. An internet telephone 130 corresponding to the receiving part receives and restores the voice packet transmitted from the sending part via the internet network 105.
First, the internet telephone corresponding to the sending part includes a microphone 101 for receiving the voice of a caller to output an analog voice signal, an analog/digital converter(ADC) 102 for converting the analog voice signal outputted from the microphone into a digital voice signal, a voice encoder 103 for compressing and encoding the converted digital voice signal, and a protocol processor 104 for processing the compressed and encoded voice data according to an internet protocol to output it in the form of a voice data packet.
Meanwhile, the internet telephone corresponding to the receiving part includes a protocol processor 106 for receiving the voice data packet transmitted via the internet network 105 and separating the compressed and encoded voice data from the voice data packet, a voice decoder 107 for restoring the compressed and encoded voice data to the original voice digital signal, a digital/analog converter(DAC) 108 for converting the restored digital voice signal into the original analog voice signal and a speaker 109 for outputting the analog voice signal as the original voice of the caller.
The operation of the internet telephones thusly constructed according to the conventional art will now be described below.
When the voice of the caller is inputted into the microphone 101 of the sending part, the analog voice signal of the caller outputted from the microphone 101 is converted into a digital voice signal by the analog/digital converter 102.
The digital voice signal outputted from the analog/digital converter 102 is converted into compressed and encoded data through the voice encoder 103 in order to increase transmission efficiency. A header, trailer, etc. are added to the compressed and encoded voice data by the protocol processor 104.
Therefore, the protocol processor 104 outputs a voice data packet. The voice data packet is transmitted toward the internet telephone corresponding to the receiving part via the internet network 105.
The voice data packet transmitted via the internet network 105 is firstly inputted into the protocol processor 106 of the receiving part. The protocol processor 106 extracts the compressed and encoded voice data from the received voice data packet by removing added information such as the header and trailer.
The extracted compressed and encoded voice data is restored to the digital voice signal by the voice decoder 107. The digital voice signal is converted into the analog voice signal by the digital/analog converter 108.
The analog voice signal is inputted into the speaker 109 and the speaker 109 outputs the original voice of the caller.
The conventional internet telephone has the following problems.
When the voice data packet transmitted or received via the internet network is partially lost during transmission or in a signal processing process, the speech quality of a VOIP(voice over internet protocol) is drastically decreased.
In other words, in the case where the voice data packet is partially lost, at the receiving part, a blank is generated in the analog voice signal of the caller as much as the lost portion of the voice data packet, and, further, the voice of the caller outputted through the speaker of the receiving part is made discontinuous.
Accordingly, the speech quality of the VOIP is drastically decreased.